NEW DELHI: The IGI Airport has for the first time been witnessing GPS spoofing for the past two-three days, leading to flights being impacted whenever easterlies blow, requiring aircraft to land from the Dwarka side and take off towards Vasant Kunj.
Earlier this year, the instrument landing system (ILS) of the airport's warhorse main runway, 10/28, was withdrawn when it was closed for upgradation to Category III to enable landings in the winter fog from both ends. Without ILS, aircraft can land making use of ‘required navigation performance' (RNP) and don't need to rely on ground-based navigation aids.
However, RNP requires GPS, and with spoofing affecting the latter, starting about 60 nautical miles from IGIA, flight movement on the main runway gets affected. It has caused congestion at a time when IGIA is seeing a spurt in air traffic, with up to 1,550 daily aircraft movement. Tuesday night saw five aircraft of IndiGo and two of Air India, among others, diverted to Jaipur for this reason.
Mitigating the impact of the new phenomenon of GPS spoofing at India's busiest airport will require promulgating ILS on runway 10/28 at the earliest. Delhi International Airport Ltd (DIAL) is working towards this, but sources said it is expected to happen by Nov 27.
IndiGo had recently carried out a trial flight on runway 10/28 to test the new system installed after the airstrip got a new approach lighting system. The report has been submitted to the Directorate General of Civil Aviation. "ILS promulgation on the runway needs to be expedited as Nov 27 is a good three weeks away," said a source.
Broadly speaking, airlines face two types of GPS issues — jamming, usually done by the military in war zones to avoid giving away location of military assets like aircraft; and spoofing, done by troublemakers in conflict zones, from Pakistan to the Middle East, Turkey and Ukraine, to confuse pilots. Spoofing ends up corrupting the GPS signals, giving pilots wrong indications about their location. The corrupted information could be off by anywhere up to 2,500km.
Airlines have devised measures to mitigate the impact of spoofing by alerting pilots in advance about the likelihood of facing this issue and advising them to switch over to alternative navigation mechanisms when they do so.
Aviation authorities said they are aware of the situation and are looking at measures to tackle the problem. "Why GPS spoofing is happening could be a security-sensitive issue, and we don't want to know why the same is happening. The only thing that needs to be done is having ILS on IGIA's main runway 10/28 at the earliest," said another source.
The ILS upgrade on the main runway took place to have the system on its both ends — it wasn't available earlier on the Dwarka side or runway 10 end —and to overall enhance capacity and build resilience.
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